[Sync] Refactoring of sync integration test checkers to remove boilerplate await methods.

chrome/browser/sync/test/integration/migration_waiter.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_SYNC_TEST_INTEGRATION_MIGRATION_WAITER_H_
 #define CHROME_BROWSER_SYNC_TEST_INTEGRATION_MIGRATION_WAITER_H_
 
+#include <string>
+
 #include "base/macros.h"
 #include "chrome/browser/sync/test/integration/status_change_checker.h"
 #include "components/sync/base/model_type.h"
 
 class MigrationWatcher;
 
 // Helper class that checks if the sync backend has successfully completed
 // migration for a set of data types.
 //
 // Collaborates with the MigrationWatcher, defined above.
 class MigrationWaiter : public StatusChangeChecker {
  public:
   // Initialize a waiter that will wait until |watcher|'s migrated types
   // match the provided |exptected_types|.
   MigrationWaiter(syncer::ModelTypeSet expected_types,
                   MigrationWatcher* watcher);
 
   ~MigrationWaiter() override;
 
-  // Implementation of StatusChangeChecker.
+  // StatusChangeChecker implementation .
   bool IsExitConditionSatisfied() override;
   std::string GetDebugMessage() const override;
 
-  // Function to trigger the waiting.
-  void Wait();
-
   // Callback invoked by our associated waiter when migration state changes.
   void OnMigrationStateChange();
 
  private:
   // The MigrationWatcher we're observering.
   MigrationWatcher* const watcher_;
 
   // The set of data types that are expected to eventually undergo migration.
   const syncer::ModelTypeSet expected_types_;
 
   DISALLOW_COPY_AND_ASSIGN(MigrationWaiter);
 };
 
 #endif  // CHROME_BROWSER_SYNC_TEST_INTEGRATION_MIGRATION_WAITER_H_